- Rhabdomyolysis is defined as skeletal muscle breakdown resulting from injury.
- Injury may result from many causes including trauma, infection, medications, or inherited disorders.
- Classic presentation is with a triad of myalgia, weakness, and dark or reddish brown urine.
- Characterized by elevated creatine kinase (CK) and myoglobinuria
- Release of intracellular contents from damaged muscle cells may cause severe electrolyte disturbances including life-threatening hyperkalemia, hyperphosphatemia, and hypocalcemia.
- The resulting myoglobinuria can cause obstruction of renal tubules and pigment-induced acute kidney injury (AKI), the most serious complication of rhabdomyolysis.
- Rhabdomyolysis is more common in adults than children, where it is commonly due to illicit or prescription drugs or due to trauma.
- Rhabdomyolysis is a common clinical problem in a catastrophic disaster (e.g., an earthquake).
- Rhabdomyolysis accounts for 7–10% of cases of AKI in the United States.
Muscle enzyme deficiencies, muscular dystrophy, and disorders of mitochondrial metabolism increase the risk of rhabdomyolysis.
- The most common causes of rhabdomyolysis in children are:
- Viral myositis: This is the most common cause for young children. Influenza A and B, Epstein-Barr virus, cytomegalovirus, and HIV have all been associated with rhabdomyolysis.
- Exercise: This is the most common cause for 9- to 18-year-olds. Exercise which is novel, intense, or prolonged, and especially in the presence of extremely hot weather may cause rhabdomyolysis.
- Trauma: Muscle trauma may occur from crush injury, compartment syndrome, or electric shock.
- Autoimmune myopathy: juvenile dermatomyositis or polymyositis
- Drugs: Illicit drug use including alcohol (alcohol withdrawal syndrome), cocaine, heroin, amphetamines, phencyclidine (PCP), and ecstasy have been associated with rhabdomyolysis.
- Causative prescription medications include lipid-lowering drugs (statins, fibrates) and antipsychotic medications (due to neuroleptic malignant syndrome).
- Less common causes of rhabdomyolysis in children include the following:
- Myopathies involving muscle enzyme or energy substrate deficiencies: These include disorders of lipid metabolism (e.g., carnitine palmitoyltransferase II deficiency), disorders of glycogenolysis (e.g., phosphorylase kinase deficiency, McArdle disease), disorders of glycolysis (lactate dehydrogenase deficiency), and mitochondrial deficiency disorders. Usual triggers for rhabdomyolysis in such conditions are fasting, exertion, or viral illness.
- Dystrophinopathies: Rhabdomyolysis is more likely to occur after exertion in association with all forms of muscular dystrophy.
- Muscle hypoxia: prolonged immobilization or loss of consciousness; certain metabolic and electrolyte disorders: hypokalemia, hypophosphatemia, hypocalcemia, and hyperosmolar states such as diabetic ketoacidosis
- Body temperature changes (hyperthermia and hypothermia): Malignant hyperthermia is a rare inherited condition that results in hyperthermia, muscle breakdown, and subsequent rhabdomyolysis on receiving halogenated hydrocarbon–containing anesthetics or muscle relaxants such as succinylcholine.
- Neuroleptic malignant syndrome: a rare neurologic disorder characterized by hyperthermia, rhabdomyolysis, and autonomic changes in patients receiving neuroleptic or antipsychotic medications
- Certain toxins: snake bite, spider venom and vespid venoms, quail, and some mushrooms
- The list of causes of rhabdomyolysis above is not exhaustive. Any child with sudden onset of muscle pain, tenderness, or weakness should be suspected of having rhabdomyolysis and any child with dark or reddish brown urine suspected of myoglobinuria.
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